Cleaning devices for printing machines are known in general, for example, from U.S. Pat. No. 3,084,626. In this known apparatus, the guide elements are situated at a distance next to the spray jets, so that they do not limit the spray jet but only prevent fluid particles from unintentionally spraying on adjacent machine parts.
Further, U.S. Pat. No. 3,900,003 discloses a fluid application apparatus for applying developer fluid on a cylinder in a multi-color electrophotography copying machine. The AT-PS 282 662 discloses a damping cylinder, which has a cylinder section that dips into a container with cleaning fluid and a section which adjoins the cylinder of a printing machine that is to be cleaned. The cleaning fluid for rinsing the damping cylinder is sprayed on the area of the damping cylinder that rises above the fluid. This is done by means of two neighboring doctor blades at a distance from one another. DE-PS 12,40,885 discloses a suction box opposite an impression cylinder. The suction box can be pivoted about an axis parallel to the cylinder and forms a gap with the cylinder. Brushes are provided on the suction box at the gap inlet and at the gap outlet. In the region between these brushes, the suction box has suction holes for suctioning dust from the surface of the paper that is to be printed and which runs around the cylinder surface. German Utility Patent 1,996,060 discloses an apparatus for spraying fluid into the gap between two rolls in the printing mechanism of an offset printing machine, in order to moisten its printing plates. The delivery of fluid is controlled in pulse-like fashion by a control device of the printing machine, depending on the printing speed and a selectable factor, as well as on a selectable spray timing. Further, DE-OS 34 46 757 A1 discloses a coating device for coating paper webs. This device forms an ink-application back-up space opposite the paper web that is being guided by the cylinder. This space is equipped with a labyrinth overflow seal against the direction of rotation of the paper web and of the cylinder.
Cleaning devices of this type are used to dissolve the dirt which collects during the printing process and which adheres to the cylinder surface. With customary rotary printing machines, a doctor blade or a cloth which absorbs the dirt with solvent is used to remove the dirt that has been softened by the cleaning fluid. With web-fed rotary printing machines, the dirt is also removed directly by the web when the cylinder that is being subjected to the cleaning process is in direct contact with the unwinding web. Several principles are thus known for transferring the cleaning fluid to the convex cylinder surface. One principle is based on application by a damping process, and various saturated materials can be used for this. Another principle is based on the application of cleaning fluid with bristles or bristle rollers, with which the dirty convex surface is cleaned mechanically at the same time. Another principle is based on spraying cleaning fluid on the convex surface of the cylinder, in which the cleaning fluid is conveyed by its inherent pressure or by the pressure of a gaseous carrier medium.
The principle of spraying is widespread, because the spraying device, in contrast to the contacting application devices, does not come in contact with the dirt and furthermore can be switched on and off easily. The duration and power of the jet can also be adjusted easily. The disadvantage of spraying is that the surface which is being cleaned and which moves underneath the jet sometimes is not wetted as well as with damping devices. Furthermore, the rebound or splatter effects and evaporation of the washing fluid occur, as a result of which portions of the fluid intended for the convex cylinder surface are lost. The fluid quantities which do not make a hit and which do not moisten the cylinder reach undesirable points of the printing machine and sometimes cause undesirable effects such as corrosion or interference with the printing carrier. The fluid which causes undesirable wetting collects in remote moistened points and forms droplets which can reach the printing carrier.
The waste of cleaning fluid is also unavoidable for kinematic reasons, because the motion and the forces of the fluid jet towards the rotating cylinder do not yield a perfect transfer of fluid into a wetting film. Droplets which strike the surface of the cylinder bounce off at various angles.